The present invention relates to components for internal combustion engines particularly, although not exclusively, to a tubular component for transferring exhaust gases between an exhaust manifold and an inlet manifold where exhaust gases are cooled during transfer between the exhaust manifold and the inlet manifold.
It is known in the prior art to use exhaust gas re-circulation systems as part of an internal combustion engine. An exhaust gas re-circulation system transfers exhaust gas from an exhaust manifold, returning the exhaust gas to an inlet manifold on the engine block allowing the returned gas to re-enter a combustion chamber. The purpose of an exhaust gas re-circulation system is to reduce formation of NOX during the combustion process. A cooled exhaust gas re-circulation system achieves this by taking exhaust gas from an exhaust manifold, and cooling the gas during transfer between the exhaust manifold and an inlet manifold thus giving a dense charge of gas returned to the inlet manifold for introduction into an inlet charge prior to combustion.
Prior art exhaust gas re-circulation systems incorporate a multi-component system including a plurality of tubular elements including a cooling element. Commonly the cooling element is substantially straight and hence difficult to package around the internal combustion engine. FIG. 1 herein illustrates a prior art exhaust gas re-circulation system. This system incorporates a first tubular section 100 attached to an exhaust manifold by fastening means at a first end 107 and a second tubular section 111 attached to an inlet manifold at a second end 108. Referring to FIG. 1, exhaust gases entering tube 100 at first end 107, the direction of exhaust gas flow being indicated by arrows, are transferred to a cooler 102. This may occur through one or a plurality of bends 101 in tube 100 of the exhaust gas re-circulation system. Within the exhaust gas re-circulation system there exists a cooler section 102. This is a separate component joined to the first and second tubes 100, 111 at points 109 and 110. Cooler 102 consists of a heat exchanger housing a plurality of tubes 105 extending the length of cooler 102. The plurality of tubes 105 are illustrated in FIG. 1(B) which shows a section of cooler 102. Each tube 105 has a diameter in the region of 6 mm. The Cooler 102 may contain an average of 30 such tubes although in some instances this amount may be as great as 60. Cooler 102 further comprises an inlet 104 and outlet 103 which permit coolant medium to enter a chamber surrounding the plurality of smaller tubes 105, thus permitting heat exchange between the gasses passing through the tubes 105 and the surrounding coolant medium. Inlet 104 and outlet 103 are further connected to pipework and fittings of the internal combustion engine cooling system. Such a system commonly incorporates a radiator. Coolant medium within the cooler 102 is not permitted to enter the first or second tubes 100, 111, the coolant medium being restricted to the length of the cooler 102.
In prior art exhaust gas re-circulation systems employing a cooler 102 there is a significant loss of efficiency due to blocking of tubes 105 by sooty deposits, commonly being acidic deposits, which are formed in the tubes 105 due to condensation of partially or non-combusted fuel. Diesel fuel, includes sulphur based compounds which can form highly acidic compounds on partial combustion. Such deposits may therefore corrode and block the tubes 105. Such corrosion and blockage means that the performance of the cooler 102 deteriorates significantly over time. A considerable loss in efficiency is seen within the first five hours of operation of such a prior art exhaust gas re-circulation system with up to 20% reduction in efficiency occurring in this period due to coating and/or blockage of the tubes 105. Therefore, prior art exhaust gas re-circulation systems lose efficiency and begin to corrode on first use. Use of higher grade materials to counter corrosion is hampered by the cost of the solutions when applied to a prior art multi-tube design.
A further disadvantage of prior art exhaust gas re-circulation systems is that cooler 102 is commonly of the order of 100 mm to 300 mm in length. As the levels of required emissions from internal combustion engines, particularly those used in cars, decrease and as the need for employing such systems on small cars to ensure low levels of emissions increases manufacturers are commonly finding that there is not enough space to conveniently package prior art coolers which require significant room in which to fit the long, straight cooler 102.
One object of the present invention is to provide a single piece component for use as an exhaust gas re-circulation system for transferring exhaust gases from an exhaust manifold to an inlet manifold of an internal combustion engine, whilst cooling the exhaust gases during transfer.
A second object of the present invention is to provide an exhaust gas re-circulation system for an internal combustion engine including a self-cleaning mechanism to prevent blockage of tubes which are transferring exhaust gases.
A third object of the present invention is to provide an exhaust gas re-circulation system where heat exchanged between exhaust gases and a coolant medium, occurring indirectly through a tubular wall, can take place substantially along the entire length of said exhaust gas re-circulation system.
A fourth object of the present invention provides for an exhaust gas re-circulation system with a decreased number of tubular members required to provide for heat exchange with a surrounding coolant medium, whilst providing an effective surface area for heat exchange which provides for at least comparable cooling of exhaust gases when compared to prior art coolers.
A fifth object of the present invention is to provide a low weight, low cost exhaust gas re-circulation system for an internal combustion engine.
According to a first aspect of the present invention there is provided a component for transferring gases between an inlet port and an outlet port of an internal combustion engine said component characterized by comprising:
a substantially tubular outer member having a first end and a second end, and an outer tubular wall extending between said first and second ends; and
a plurality of substantially tubular inner members housed in said first substantially tubular outer member, wherein said second substantially tubular inner members are corrugated along at least part of their length.
Preferably said plurality of substantially tubular inner members extend substantially an entire length of said substantially tubular outer member between said first and said second ends.
Said plurality of substantially tubular inner members may comprise a plurality of tubular sections, each following a curved path.
Preferably said first substantially tubular outer member is corrugated throughout at least one portion.
Preferably said first substantially tubular outer member contains apertures suitable for inlet and outlet of a coolant medium.
Preferably said first and second ends of said outer tubular member are substantially blocked in order to retain coolant medium within said first substantially tubular outer member, save for apertures remaining to permit gas flow into each of said plurality of substantially tubular inner members.
Said plurality of substantially tubular inner members may be mounted through at least one spacer maintaining said substantially tubular inner members at substantially fixed position s relative to each other.
Said outer tubular member may be substantially bent to a required shape.
In one embodiment, said substantially tubular outer member is manufactured from metal tubing with a wall thickness in the region of 0.3 to 0.5 mm; and
said substantially tubular inner members are manufactured from metal tubing with a wall thickness in the region of 0.2 to 0.3 mm.
Said first and second ends may comprise flanges with apertures for inserting fastening means to fasten said tub e to s aid engine, forming a gas-proof seal using a gasket.
The invention includes an internal combustion engine having an exhaust gas re-circulation system, said system including means for cooling and transferring gases wherein said means comprises:
a substantially tubular outer member having a first end and a second end;
a plurality of substantially tubular inner members housed in said first substantially tubular outer member;
wherein said substantially tubular inner members are corrugated along at least a part of their lengths.
Said first substantially tubular outer member preferably includes suitable apertures wherein a coolant medium can be circulated externally of said substantially tubular inner members, said coolant medium flowing in a circuit comprising:
said exhaust gas re-circulation system;
a radiator; and
a pump, coolant storage vessel, pipework and fittings associated with said radiator, wherein said apertures connect said exhaust gas re-circulation system and said pipework to form a coolant circuit for passage of said coolant over said plurality of inner members.
Said first end of said substantially tubular outer member may be located at an exhaust manifold and said second end may be located at an inlet manifold wherein in operation of said engine coolant medium in said tube is restricted between said first and second ends and externally of said substantially tubular inner members, inlet and outlet of coolant medium from said tube occurring through inlet and outlet apertures.
Preferably said tube forms a single part for fitment to said engine, said tube being pre-bent to a specific configuration to provide economy of space when fitted to said engine.
In a preferred embodiment, said substantially tubular outer member has a metal wall thickness in the region of 0.3 mm to 0.5 mm.
Preferably, when fitted to an internal combustion engine, said first end of said substantially tubular outer member is fixed during operation at a vertically higher fixed point to said second end, both of said ends comprising flanges with apertures for inserting fastening means in order to fix said tube to said engine forming a gas-proof seal using a gasket.
According to a second aspect of the present invention there is provided a method of assembly of a tube for an internal combustion engine said method comprising the steps of:
locating a plurality of plates along the length of a plurality of corrugated substantially tubular inner members;
placing said combination of said plates and said plurality of substantially tubular inner members within a substantially tubular outer member; and
fixing said plates in position.
Said method preferably further comprises the step of fastening said substantially tubular outer member to an internal combustion engine and radiator system.
According to third aspect of the present invention there is provided a method of cooling exhaust gases for an internal combustion engine exhaust gas re-circulation system said method comprising the steps of:
directing an exhaust gas flow into a plurality of corrugated substantially tubular members;
forming a turbulent flow of said exhaust gas within said corrugated substantially tubular members;
wherein heat exchange occurs through at least one substantially tubular wall of said plurality of corrugated substantially tubular members with a surrounding coolant medium.
In use, said gas flow may experience a decrease in velocity of gas flow within said plurality of corrugated members.
Whilst transferring said exhaust gases to an inlet manifold, small particulate matter may be driven through said plurality of corrugated substantially tubular members. The gases may form a turbulent flow within the corrugated tubular members.
During the passage of gases through the corrugated tubular member, heat is exchanged from said surrounding medium through a surrounding outer tubular wall to an external environment.